The National Trust for Scotland intends to seek donations from supporters in the US for its new Culloden Battlefield Memorial Centre.
Appeal letters and leaflets have been sent to trust members
It is part of a wide-ranging strategy to meet a £1.65m funding shortfall.
The trust said it knows for sure it has raised £150,000 so far from a separate UK appeal to find 1,000 donors willing to give £500 each towards the centre.
NTS said it enjoys huge support from people in America and plans to launch a fund-raising drive in the US soon.
The trust has been trying to ensure the completion of the building in time for the 2007 Highland Year of Culture.
Last month it launched its appeal in search of 1,000 donors who wished to give £500 each towards the centre.
Letters were sent to trust members from new chairwoman Shonaig Macpherson, who hoped £500,000 could be generated by Friday.
Karen Reid, head of fundraising at the NTS, confirmed £150,000 was raised in the first week of this appeal and said more donations were due to be totted up.
She said: "The response so far has been excellent.
"In the first week of the appeal we raised £150,000 towards the Culloden Battlefield Memorial Project and donations are still coming in.
"We are extremely grateful to those people who have already donated to the appeal as their support will help us tremendously.
"However, we still need a lot more help if we are to reach our target of £500,000 and I hope that many more people will want to be part of this important project."
On other efforts to plug the £1.65m gap, she said: "The fundraising effort for Culloden will continue until we have raised enough money to support the project.
"We are planning a number of events, to be announced later in the year, which will help us raise the profile of Culloden and the project.
"We also intend to appeal for help from people in the US as there are many people overseas who care deeply about Scotland's heritage and they can play an important role in the development of a fitting memorial at Culloden."
The new building will replace the existing one which the trust said attracts more than 250,000 visitors a year.
Culloden Moor was the scene of the last major battle fought on mainland Britain.
The battle took place on 16 April, 1746 and effectively ended Jacobite hopes of restoring the exiled Stuart dynasty to the throne of Britain.
The army of Prince Charles Edward Stuart was crushed by government forces led by the Duke of Cumberland in less than an hour.